Acceptability of policies targeting dietary behaviours and physical activity: a systematic review of tools and outcomes

Abstract Background Successful implementation of health policies require acceptance from the public and policy-makers. This review aimed to identify tools used to assess the acceptability of policies targeting physical activity and dietary behaviour, and examine if acceptability differs depending on characteristics of the policy and of the respondents. Methods A systematic review (PROSPERO: CRD42021232326) was conducted using three databases (Science Direct, PubMed and Web of Science). Results Of the initial 7780 hits, we included 48 eligible studies (n = 32 on dietary behaviour, n = 11 on physical activity and n = 5 on both), using qualitative and quantitative designs (n = 25 cross-sectional, quantitative; n = 15 qualitative; n = 5 randomized controlled trials; n = 3 mixed-methods design). Acceptability was analysed through online surveys (n = 24), interviews (n = 10), focus groups (n = 10), retrospective textual analysis (n = 3) and a taste-test experiment (n = 1). Notably, only 3 (out of 48) studies applied a theoretical foundation for their assessment. Less intrusive policies such as food labels and policies in a later stage of the implementation process received higher levels of acceptability. Women, older participants and respondents who rated policies as appropriate and effective showed the highest levels of acceptability. Conclusion Highly intrusive policies such as taxations or restrictions are the least accepted when first implemented, but respondents’ confidence in the relevance and effectiveness of the policy may boost acceptability over the course of implementation. Studies using validated tools and a theoretical foundation are needed to further examine opportunities to increase acceptability.


Introduction
U nhealthy dietary behaviours and a lack of physical activity have been recognized as the main risk factors contributing to the increasing prevalence of non-communicable diseases such as cardiovascular disease, diabetes and cancers. 1 Therefore, policies targeting dietary behaviours and physical activity, such as the provision of information or measures that restrict choice by regulation are important levers for reducing the global burden of disease. 2 For public health policies to be effective, it is critical that they are accepted by the public 3 as well as policy-makers. 4 Acceptability of policies can be defined as the perception among stakeholders that the implementation of a given policy is agreeable, palatable or satisfactory. 3 While acceptability of policies has been studied in domains such as tobacco control and alcohol consumption, there is a need for further research on acceptability of policies in the domains of physical activity and diet. 5 An older systematic review by Diepeveen et al. 5 on public acceptability of government interventions examined various health behaviours, but diet and physical activity accounted only for a small proportion of policies analysed, and many have been studied and reported since.
Acceptability towards policies targeting dietary behaviours and physical activity may vary with characteristics of the policies and of the respondents (target population and/or policy-makers). 5 According to the 'Nuffield intervention ladder', policies can be classified according to their degree of intrusiveness. 6 Policies higher up the ladder are more intrusive (i.e. more restrictive) and are often perceived less acceptable as they tend to reduce one's individual freedom. Acceptability is higher for less intrusive policies such as health media campaigns or warning labels. 5 Acceptability can also vary with the stage of implementation, 5 with policies in a later stage tending to be better accepted. Acceptability can be of key relevance across all stages of implementation: In an early stage, acceptability is crucial for the initial adoption, in an ongoing stage, it is needed for a successful integration into service settings. In a later stage, acceptability impacts the sustainability of a policy. 3 Acceptability may also vary with characteristics of the target respondents. Diepeveen et al. 5 found that women and older participants reported the highest levels of acceptability. The evaluation of acceptability can be studied in various ways but has been predominantly conducted through online surveys and questionnaires. 7 Data on the validity and reliability of these measures are largely missing, with some exceptions, such as the Acceptability of Intervention Measure. 8 The aim of this review was 2-fold: First, to identify tools used for assessing and evaluating acceptability of policies targeting physical activity and dietary behaviours. Secondly, to examine the acceptability of policies that relate to dietary and physical activity behaviours, and the role of policy and respondent characteristics on acceptability.
The present review was conducted within the Policy Evaluation Network (www.jpi-pen.eu). 9 Since 2019, 28 European research institutions have collaborated in this network to advance knowledge on the effective implementation of policies and their impact in terms of improving health behaviours. In this review, we build on the previous work of Diepeveen et al., 5 extending that review to the focus areas of the Policy Evaluation Network by shifting the scope to dietary and physical activity behaviours to identify tools to analyse acceptability.

Methods
We conducted a systematic review to identify and summarize (i) relevant literature on the acceptability of policies devised to target dietary and physical activity behaviours, and (ii) evaluation methods to assess acceptability. This review was conducted and reported according to the current PRISMA guidelines. 10,11 Search strategy The primary search covered three databases: Science Direct, PubMed, Web of Science and Google Scholar. The search strategy included a range of behaviour-related keywords used in combination with policy (or related terms such as regulation, law, intervention) and keywords indicating the assessment of acceptability (e.g. support, opinion), which were customized to each database (see Supplementary material S1a: search strategy). We searched for studies published in English between 2010 and 2021 and reviewed bibliographies of the included studies to check for further relevant references.

Study selection and inclusion criteria
We included original studies that explored acceptability towards a policy targeting dietary and/or physical activity behaviours. Studies were eligible if they investigated political acceptability, i.e. the perspective of individuals involved in the decision-making process and/ or public acceptability, from the perspective of individuals potentially affected by a policy. 4 We defined key terms in advance to facilitate and standardize the identification of studies (see Supplementary material S1b: inclusion criteria).
The inclusion of studies was decided upon in an iterative and hierarchical manner by two reviewers, starting out with the initial evaluation of study titles and the screening of abstracts, with full-text evaluations as the final step. The final inclusion of studies was based on two independent raters (A.S.M.-S., A.N.-P., D.A.S., J.W., K.L., K.W.-T., M.S. and S.F.) for each identified record, and any disagreements were discussed until consensus was reached.

Quality assessment
The quality of the included studies was assessed using the Critical Appraisals Skills Programme (CASP) for qualitative studies and randomized controlled trials, 12 and the National Institutes of Health (NIH) Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. 13 The quality appraisal was independently performed by two reviewers for each study (M.S., D.A.S., J.W., B.M. and K.L.), any disagreement was resolved by consensus.

Data extraction and synthesis
The following data were extracted from each study: study design, sample, data collection and analysis methods and results. Five categories of information were coded and extracted: (1) All types of measures used to gain information on acceptability; (2) Levels of acceptability; (3) Characteristics of target behaviour; (4) Characteristics of policies: the type and content of policies, the target population, intrusiveness of the intervention according to the Nuffield Intervention Ladder 6 and stage of implementation (early, ongoing, late) 3 ; and (5) Characteristics of target respondents: age, sex, country and socioeconomic status.
Two researchers independently extracted the data from included studies (M.S., B.M., J.W. and D.A.S.). Given the heterogeneity of the study methods and data, we opted for a narrative synthesis of the extraction outcomes. The synthesis was conducted by two researchers (T.K. and M.S.). Any disagreements during the data synthesis process were resolved by the consensus method. 14 We mapped the included studies according to: (i) study type; (ii) data collection method; (iii) characteristics of policies; and (iv) characteristics of target respondents. Quantitative data synthesis followed the Synthesis without Meta-Analysis guidelines. 15 To synthesize results on levels of acceptability, a vote counting on the direction of effect was conducted by two reviewers (M.S. and T.K.). Detailed vote counting results are included in Supplementary material S2.

Results
The PRISMA Flow chart illustrates the inclusion and exclusion of studies (figure 1). Our search identified a total of 7780 publications. Duplicates (n ¼ 544) were automatically removed. A total of 7070 articles did not meet the inclusion criteria and were excluded during title and abstract screening. We examined the full texts of 166 publications; 49 studies met our inclusion criteria. One of these studies 16 was excluded during data extraction, as the results section indicated an evaluation of appropriateness rather than acceptability (see Supplementary material S1b: exclusion criteria). The remaining 48 studies were included in our review. Table 1 gives an overview of study design, sample characteristics, target behaviours and data collection methods.

Quality assessment results
Two randomized controlled trials were evaluated positively on seven and two on eight out of nine points on the CASP 12 criteria. For the 15 qualitative studies, one was evaluated positively on seven, nine studies on eight and five studies on nine out of nine points of the CASP 12 criteria. The most common points that were evaluated negatively were reflexivity and the consideration of the relationship between participants and researchers. All cross-sectional, quantitative studies received a fair (10 out of 25) or good (15 out of 25) quality rating. 13 Based on the quality ratings, we decided to include all identified original studies into the review. Quality assessment results for each study are shown in Supplementary material S2. One recurring comment was the lack of a theoretical foundation for acceptability. Only three of the 48 studies used the term 'acceptability' and provided a clear definition. [17][18][19] Study characteristics Table 2 gives an overview on study designs and data collection methods used in the included studies. Besides online surveys with varying response-formats and length, we identified qualitative approaches such as interviews, focus groups and retrospective textual analyses. Table 1 provides details on the specific data collection method for each study.

Policy and target group characteristics
Across the included studies, 32 addressed dietary behaviours, 11 physical activity and 5 a combination of both. Most of the policies addressing dietary behaviour aimed at a reduced calorie intake, mostly by lowering the consumption of foods high in sugar and fats. Policies addressing physical activity aimed at preventing sedentary behaviours or promoting active forms of transportation such as walking or cycling. A detailed description of the behaviours targeted in each study is available in Supplementary material S3.

Characteristics of policies included in the review
Of the 48 included studies, 17 measured acceptability for more than one policy, comparing, for example, different policies in one policy area (e.g. three different food labels) 21 or assessing acceptability of different types of policies (e.g. campaigns, labels and restrictions). 22 For detailed information on policy type and content see Supplementary material S3.
Stage of implementation. We classified policy implementation stage according to Proctor et al. 3 into early stage (agenda setting), mid-(ongoing) stage and late stage (application) ( Table 3).
Results from three studies [23][24][25] showed that policies in a later stage received more support from both policy-makers and the target population than in earlier stages. A study conducted by Pettigrew et al. 24 compared support among school staff members for a school-food policy between 2008 and 2016 and found significantly higher levels   Themes identified: experience with implementing projects focusing on promoting physical activity and healthy diet; and key barriers and facilitators on designing, implementing and evaluating projects at the local level.
(2) Electronic survey contained both closed multiple response questions and open questions. Themes included were: experiences in projects related to the promotion of healthy habits over the last 5 years, barriers for projects 'implementation, use of process and outcome measures for projects' evaluation. (continued) Acceptability of policies targeting dietary behaviours and physical activity iv35 Acceptability of policies targeting dietary behaviours and physical activity iv39  (2) paper-based question-naire (1) Interviews: NA (2) Survey: N ¼ 4 items (1) Qualitative interviews with kitchen staff on implementation of Meatless Monday: The topics the participants emphasized during the interviews were: relevance of targeting meat, knowledge, decisionmaking processes and soldiers' attitudes.
(2) Quantitative survey on soldier attitudes to vegetarian food: (1) 'Reducing meat consumption is an efficient environmental measure', (2) 'A high level of meat consumption is harmful to health', Acceptability of policies targeting dietary behaviours and physical activity iv43  'support' Online survey N ¼ 37 items (referring to different aspects of the program) Items assessing support for menu changes and support for adding more meatless entré e on a nine-point Likert Scale (1 being 'not supportive' and 9 being 'supportive' ). and open-ended questions to receive comments/opinions.
Item example: 'Below are the proposed nutrition standards for centres enrolled in South Carolina's ABC program. Please rate your support for this change on a scale of 1 to 9 (1 being not supportive and 9 being supportive)'. In addition, parents were asked about their support for a centrespecific policy of only bringing healthy snacks for classroom celebrations.
Vargas-Meza et al. cognitive workload) Label acceptability was evaluated using three indicators: likability, attractiveness and perceived cognitive workload, based on the framework of system acceptability by Nielsen. 50 A questionnaire with ten statements was used to assess acceptability. Questions were answered by the participants using a five-point Likert scale. (continued) iv44 European Journal of Public Health (1) Individual responsibility for behaviours (e.g. providing programs to educate or motivate the general public about the importance of regular physical activity), (2) modifying community environments (e.g. the quantity and quality of green spaces, safe areas for physical activity, and the design of neighbourhoods to encourage informal physical activity), (3) targeting legislative changes to modify the environment (e.g. banning all traffic in high-use pedestrian areas during peak hours to support active or public transportation and restricting the use of elevators for trips to lower floors), focusing on economic levers (e.g. incentives, subsidies and tax credits).
a: Political, any individuals involved in the decision-making process (e.g. policy-makers, politicians and informants from ministries); public, any individuals potentially affected by an SSBs tax (i.e. the public).
b: Acceptability theme: aspects relating to acceptability in the study. c: Length refers to Item/Questions aiming at acceptability(-related concepts). AT, active transport; Diet, dietary behaviour; NA, not available; PA, physical activity; SB, sedentary behaviour. Level of intrusiveness. We rated policies according to the steps in the Nuffield ladder 6 and divided them into three groups: Highly intrusive policies (guiding choice through disincentives and eliminating/ restricting choice, n ¼ 25), moderately intrusive policies (guiding choice through incentives and by changing the default policy, n ¼ 23) and low intrusiveness (providing information and enabling choice, n ¼ 29). Eleven studies reported a tendency that highly intrusive policies received less support than less intrusive policies. 17,18,22,[26][27][28][29][30][31][32][33] For instance, Kwon et al. 29 found lower levels of support for a marketing ban on unhealthy foods (34.7%) than for subsidies on fruit and vegetables (68.2%).
A total of 15 studies investigated policies aimed at (school-)children, 10 of which were categorized as low and 5 as moderately intrusive. The policies with low levels of intrusiveness (n ¼ 10) received predominantly high levels of acceptability (8/10). For example, 86% support was found for a policy promoting active school transport, 39 while all moderately intrusive policies (n ¼ 5) received mixed (3/5) or low (2/5) levels of acceptability.
Levels of feasibility, appropriateness and perceived effectiveness. Ten studies analysed appropriateness, feasibility or perceived effectiveness as implementation outcomes in addition to acceptability. 20,28,30,[34][35][36][37][38][39][40][41] Six studies 28,30,[34][35][36][37] measured appropriateness, such as the perceived importance or relevance of the policy. 3 Findings showed that target group respondents who strongly believed that obesity was a serious problem were overall more supportive of healthy nutrition policies [beta ¼ 0.36, 95% confidence interval (CI) 0.24-0.47]. 37 Three studies explored feasibility alongside acceptability. 20,29,41 Feasibility is defined as the extent to which a policy can be successfully used or carried out within a given setting. 3 Within each of these studies, policies were perceived equally acceptable and feasible. All studies that reported on perceived effectiveness, 34,[38][39][40] found that policies which were rated highly effective, also received high levels of acceptability. For example, Pell et al., 38 found similarly high levels for acceptability (70%) and perceived effectiveness (71%) for a sugary drink tax in the UK.

Characteristics of respondents
A majority of the included studies investigated public acceptability among the policies' target populations (42/48). Three studies investigated political acceptability of policies (e.g. in samples that consisted of policy-makers), 39,42,43 the remaining two studies investigated both political and public acceptability. 22,28 The primary studies were predominantly from North America (18/48) and Europe (18/48), the remaining studies originated from Central and South America (6/48) and Oceania (6/48). Table 1 provides an overview on sample characteristics for each study. For further details on samples including country of origin, see Supplementary material S3.
Political vs. public acceptability. Four studies identified a lack of acceptability as a significant barrier to implementation 28,40,41,44 and high acceptability as a facilitator among policy-makers, for the implementation of policies. 39 One study reported higher levels of support from policy influencers (80%) than from the public (63.3%) towards healthy eating policies. 28 Gender, age and socioeconomic status of respondents. Ten studies reported gender differences, with women generally showing higher levels of acceptance towards policies regardless of target behaviour or policy type. 17,18,25,29,33,35,37,[45][46][47] Moreover, three studies found that compared to male target respondents, women showed a tendency to be more supportive of more intrusive policies such as salt limits, 45 restrictions to limit access to high-fat foods, 35 high sugar drinks 17 or restrictions to ban traffic in certain areas to facilitate active travel. 33 Five studies found a link between acceptability and age. 25,31,33,45,48 Four out of five studies found the tendency that older participants reported relatively higher levels of acceptability than younger participants, especially for highly intrusive policies such as marketing bans for unhealthy foods. 25,31,33,45 Julia et al., 25 showed that older participants were more likely to support a soda tax than younger counterparts [odds ratio (OR) ¼ 2.37; 95% CI 1.60, 3.49 for >65 years old vs. 26-45 years old; P < 0.001]. One study showed an opposite effect for a policy promoting active transportation: Levels of support were lower among those over age 65, when compared with those in the youngest age category (18-24 years). 48 Six studies reported differences in acceptability according to socioeconomic status of the policy target population, 18,25,30,33,35,49 i.e. participants with a higher educational background rated policies to change product sizes as more acceptable than those with low education (OR ¼ 0.31; 95% CI 0.19-0.52; P < 0.001). 18 Three studies found Online survey (n ¼ 15), Paper questionnaire (n ¼ 5), Mail survey (n ¼ 2), Computer-assisted, face-toface omnibus survey (n ¼ 1), Telephone survey (n ¼ 1), Computer Assisted Telephone Interview (n ¼ 1) Semi-structured Interviews (n ¼ 6), Focus groups (n ¼ 5), Retrospective textual analysis (n ¼ 3), Combination of focus groups and interviews (n ¼ 1) Interviews and paper-based questionnaire (n ¼ 1), Semi-structured interviews and online surveys (n ¼ 1), Online survey and structured focus groups (n ¼ 1) Paper questionnaire (n ¼ 1), Online survey (n ¼ 3), Modified version of the nutrition try-day taste-testing ballot 74 (n ¼ 1) a: RCT, randomized controlled trials (n ¼ 4), randomized cross-over trial (n ¼ 1). iv46 European Journal of Public Health that taxation policies were more acceptable among lower socioeconomic groups, if they were combined with another policy action. 22,25,45 In a study conducted by Julia et al., 25 22.4% more participants reported that they would support a taxation policy, if combined with a subsidy to fund healthcare system improvements (48.5% vs. 72.7%).

Discussion
We set out to identify tools used to assess acceptability of policies targeting diet and physical activity, and to examine acceptability with regard to characteristics of the various policies. We found a wide range of different approaches and tools to study this topic.
Few studies presented a link to an existing framework or a theoretical foundation of acceptability. Two papers 17,18 defined acceptability according to the definition provided by Sekhon et al. 7 and one paper 19 based their assessment of acceptability on the framework of system acceptability by Nielsen (1993). 50 Moreover, most of the measures did not include information on the reliability and validity of the measures. Only 2 26,50 of the 38 survey studies reported on reliability. In contrast, most qualitative approaches applied a theoretical foundation to their measures such as the framework method 51 or key informant interview technique. 52

Policy characteristics
More than three quarters (32/48) of the studies included in this review analysed acceptability of policies targeting dietary behaviours, while findings including policies targeting physical activity were relatively scarce (16/48). Although policies targeting physical activity were well accepted in the included studies, there is a gap in research on the acceptability of policies targeting physical activity. This needs to be addressed by future research, as such policies have the potential to facilitate numerous health benefits including a reduction in coronary heart disease, stroke and diabetes. 1 Our findings on acceptability according to stage of implementation and intrusiveness are in line with existing literature for other health behaviours 3,5 : highly intrusive policies were generally less accepted, especially by men, younger age groups and those with a lower educational background, but acceptability by policy-makers and the target groups of the policies may increase over time. With highly intrusive policies, which are often more effective than less intrusive policies, 6 governments need stronger justification for implementation in order to achieve sufficient levels of acceptability. This is substantiated by our findings on the relationship between acceptability and other implementation outcomes: Respondents who rated the policies to be effective, appropriate or feasible also found them to be acceptable. 20,28,30,[34][35][36][37][38][39][40][41] Target group characteristics Our findings on acceptability with regard to sex, age and socioeconomic status and were largely consistent with previous research. The tendency that women are more likely to support intrusive policies has been shown for other health-related behaviours such as smoking and alcohol consumption. 5 A reason for the observed gender difference may lie in the domain of dietary behaviours, as women are more often subject to weight discrimination and may be sensitive and supportive to diet-related policies. 53 We were also able to replicate the finding of Diepeveen et al., 5 that acceptability seems to increase with age. This was particularly true for highly intrusive policies. 17,35,45 An exception was a study conducted by Gase et al., which found higher support among younger participants towards a policy re-directing transportation funds to active transport than among older participants. 48 This may be due to younger individuals more often relying on alternatives to cars as means of transportation, such as bicycles. 54 Six studies reported on levels of acceptability varying with socioeconomic status of the respondents. 18,25,30,33,35,49 A majority found less support among groups with lower socioeconomic status for pricing and taxation policies, 25,30,33,35,49 possibly because they were economically more affected that individuals with higher income. Moreover, we found that taxation policies were more popular among lower socioeconomic groups, when they were combined with a subsidy, 25,45 e.g. for produce. 22 This information may be useful when considering taxation policies in the future. Overall, we observed a lack of research addressing equity-and diversity-related factors: Samples were predominantly White, highly educated, and from middle-to high-income countries such as the USA and Europe. Few studies mentioned this as a limiting factor and fewer drew conclusions on the acceptability of policies in minority groups. 29,55 Strengths and limitations of the current review To our knowledge, this is the first systematic review to comprehensively map evidence on public and political acceptability focusing on dietary and physical activity behaviours. We identified a variety of tools to measure acceptability and were able to identify gaps in the existing research and ways to strengthen future studies. There are limitations to our findings: Because of the heterogeneous designs, the large variety in assessment methods and heterogeneous answer formats, data of our literature search were not well suited for quantitative synthesis via meta-analytic procedures.
Another weakness of our review is the limited search range. We restricted ourselves to searching electronic, scientific databases excluding grey literature and political documents. This may be a reason why research and findings on political acceptability may be not well represented in our studies.

Implications for policy-makers
Our findings show that intrusive policies are generally less well accepted, but become more accepted with time. This needs to be considered when facing decisions to implement particularly unpopular yet potentially highly effective policies. Over time, people may get used to the measures implemented by governments and become more accepting of such policies. Moreover, findings on appropriateness indicate that people who recognize the relevance of policies, e.g. because they are aware of the risks of certain behaviours, show a higher support of government action. Therefore, it is crucial that policy-makers provide well-communicated justifications for policies.

Implications for research on policy acceptability
In order to monitor acceptability reliably both from a political and public perspective, we would recommend further research to consider three steps to increase quality and meaningfulness of publications: (1) The use of a pre-set definition of acceptability and further included terms and outcomes based on scientific theories/models, such as the framework provided by Proctor et al. 3 (2) The use of reliable, validated tools based on a framework such as the Acceptability of Intervention Measure. 8 (3) The inclusion of more diverse samples in terms of socioeconomic status, ethnicities and cultural backgrounds to gain a more holistic societal perspective.
Since we found a notable imbalance in target groups (public vs. political) and behaviours (dietary behaviour vs. physical activity), further research should aim at including the political perspective more broadly and to expand research activities on acceptability towards policies targeting physical activity.
Acceptability of policies targeting dietary behaviours and physical activity iv47

Conclusions
Highly intrusive policies such as taxations or restrictions are the least accepted when first implemented, but respondents' confidence in the relevance and effectiveness of the policy may boost acceptability over the course of implementation. The current evidence is mostly based on studies done in European and North American contexts. Studies using validated tools and a theoretical foundation are needed, to further examine opportunities to increase acceptability.